640377979 has 2 divisors, whose sum is σ = 640377980. Its totient is φ = 640377978.

The previous prime is 640377977. The next prime is 640378001. The reversal of 640377979 is 979773046.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 640377979 - 2¹ = 640377977 is a prime.

Together with 640377977, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (640377977) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320188989 + 320188990.

It is an arithmetic number, because the mean of its divisors is an integer number (320188990).

Almost surely, 2^640377979 is an apocalyptic number.

640377979 is a deficient number, since it is larger than the sum of its proper divisors (1).

640377979 is an equidigital number, since it uses as much as digits as its factorization.

640377979 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2000376, while the sum is 52.

The square root of 640377979 is about 25305.6906445961. The cubic root of 640377979 is about 861.9434949315.

The spelling of 640377979 in words is "six hundred forty million, three hundred seventy-seven thousand, nine hundred seventy-nine".